My wife bought me the RiverWest BackCountry pants and jacket last christmas and I used it alot until the end of february. This stuff is nothing short of awesome. It is super thin and very warm, I will not walk with it on however. Its so warm I sweat if I walk with it on. I wear my baselayers, and pack this stuff in on my climber. I climb the tree and put it on over my baselayers and harness and I'm toasty and have pretty thin clothing. I've never been warmer and it is completely waterproof, and thorn proof, and it has a 10-year warranty. You can't hardly rip it, tear it, etc.

Now what I got was the Lightweightversion, I can't image using the original, warmer stuff here.I wear my thin baselayers with the Rivers West over it if its down to around 30-35 degrees and if its colder than that, I put on a very thin fleece pants and shirt to keep my warm down to around 10 degrees.
I love it.